1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
10 use crate::consts::{constant_simple, Constant};
11 use crate::rustc::hir::*;
12 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
14 use crate::rustc::{declare_tool_lint, lint_array};
15 use crate::syntax::source_map::Span;
16 use crate::utils::{clip, in_macro, snippet, span_lint, unsext};
18 /// **What it does:** Checks for identity operations, e.g. `x + 0`.
20 /// **Why is this bad?** This code can be removed without changing the
21 /// meaning. So it just obscures what's going on. Delete it mercilessly.
23 /// **Known problems:** None.
27 /// x / 1 + 0 * 1 - 0 | 0
29 declare_clippy_lint! {
32 "using identity operations, e.g. `x + 0` or `y / 1`"
35 #[derive(Copy, Clone)]
36 pub struct IdentityOp;
38 impl LintPass for IdentityOp {
39 fn get_lints(&self) -> LintArray {
40 lint_array!(IDENTITY_OP)
44 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityOp {
45 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
49 if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
51 BinOpKind::Add | BinOpKind::BitOr | BinOpKind::BitXor => {
52 check(cx, left, 0, e.span, right.span);
53 check(cx, right, 0, e.span, left.span);
55 BinOpKind::Shl | BinOpKind::Shr | BinOpKind::Sub => check(cx, right, 0, e.span, left.span),
57 check(cx, left, 1, e.span, right.span);
58 check(cx, right, 1, e.span, left.span);
60 BinOpKind::Div => check(cx, right, 1, e.span, left.span),
61 BinOpKind::BitAnd => {
62 check(cx, left, -1, e.span, right.span);
63 check(cx, right, -1, e.span, left.span);
71 #[allow(clippy::cast_possible_wrap)]
72 fn check(cx: &LateContext<'_, '_>, e: &Expr, m: i8, span: Span, arg: Span) {
73 if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
74 let check = match cx.tables.expr_ty(e).sty {
75 ty::Int(ity) => unsext(cx.tcx, -1_i128, ity),
76 ty::Uint(uty) => clip(cx.tcx, !0, uty),
90 "the operation is ineffective. Consider reducing it to `{}`",
91 snippet(cx, arg, "..")